A state of mental illness or extreme confusion; or the act of throwing something into disorder.
From 'derange' + the suffix '-ment' (forming nouns describing states or conditions). This combination became common in English medical and psychological terminology during the 18th-19th centuries.
The word 'derangement' was a favorite of Victorian-era doctors and authors—you'll find it all through 'The Strange Case of Dr. Jekyll and Mr. Hyde' and other gothic fiction, used to describe the terrifying moment when someone's mind goes completely haywire.
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